Evaluation of coronary stenoses experimentally and clinically is hampered by the absence of satisfactory criteria for defining the severity of coronary lesions. The use of percent diameter narrowing does nto account for the critical geometric characteristics of stenosis length, absolute diameter, eccentricity, and shape on streamlining which may have greater effects on pressure and flow than percent stenosis. Accordingly, there are no means of comparing stenoses of differing size and shape or in different size coronary arteries, and there is no way of defining how severe a lesion must be geometrically before causing regional underperfusion, abnormal left ventricular contraction, or ischemia. Model constrictions of rigid tubes have been described by fluid dynamic equations relating genometric characteristics to flow velocity and pressure loss. However, the applicability of these fluid dynamic equations to stenoses of an artery with pulsatile pressure and flow and a distensible, vasoactive vessel wall has not been demonstrated in vivo. Over the past six years, the principal investigator has developed a chronically instrumented dog model for coronary arteriography and independent measurement of the pressure gradient-flow characteristics of variable, controlled coronary stenoses in intact, unsedated dogs. Results in this laboratory indicate that quantitative analysis of orthogonal coronary arteriograms using classical fluid dynamic equations accurately predicts the experimentally measured pressure gradient-flow characteristics of coronary stenoses. When finally developed the analysis program will consist of automatic border tracking of background subtracted arteriograms which are then processed according to the Greg Brown analysis utilized previously. In its final application the entire analysis facility will be completely automatic. Cineangiograms will be obtained during an experiment and will be projected into the digitizing equipment currently installed and appropriate films selected by the operator. All subsequent processing, border recognition, background subtraction and fluid dynamic analysis will be carried out automatically within computer memory and a hard copy printout provided of all of the fluid dynamic characteristics of the stenosis selected by the operator. The accuracy of this automated program will be tested in a series of chronically instrumented animals and then subsequently applied to human coronary arteriograms.